Association of TrkA with endogenous
GIPC in PC12 (615) cells. (A) Top, TrkA coprecipitates with endogenous
GIPC in both control (lane 1) and NGF-treated (lanes 2 and 3) cells.
Addition of 100 nM K252a, a specific Trk kinase inhibitor, before NGF
treatment had no effect on the interaction (lane 4). Little or no TrkA
is seen in precipitates obtained with preimmune serum (lanes 5 and 6).
Middle, the presence of GIPC in immune (lanes 1–4) but not preimmune
precipitates (lanes 5, 6) was verified by
immunoblotting. Bottom, an aliquot of lysate was
immunoprecipitated with anti-Trk (C-14) IgG and
immunoblotted with anti-phosphotyrosine (PY99) IgG to
verify the activation of TrkA by NGF (lanes 2 and 3). PC12 (615) cells
were cultured in low-serum–containing medium overnight and
treated with 100 ng/ml NGF for 0, 10, or 30 min. Cell lysates (3.7 mg)
were immunoprecipitated (IP) with either anti-GIPC or preimmune serum
followed by immunoblotting (IB) with anti-Trk (B-3)
(top) or anti-GIPC (middle). (B) Phosphorylated TrkA (arrowhead)
coprecipitated with endogenous GIPC at all time points (7, 30, and 60
min) after NGF treatment (lanes 3–5) but not in the untreated sample
(lane 2) or that precipitated with preimmune serum (lane 1). PC12 (615)
cells were treated with 100 ng/ml NGF as in A. Cell lysates (3.3 mg)
were immunoprecipitated with either anti-GIPC or preimmune serum
followed by immunoblotting with antiphosphotyrosine
PY99 (top) or anti-GIPC (bottom).